Primate Culture Is Just A Stone's Throw Away From Human Evolution, Study Finds

January 15, 2009 — For 30 years, scientists
have been studying stone-handling behavior in several troops of
Japanese macaques to catch a unique glimpse of primate culture. By
watching these monkeys acquire and maintain behavioral traditions from
generation to generation, the scientists have gained insight into the
cultural evolution of humans.

Primatologists Michael A. Huffman, Charmalie A.D. Nahallage, and
Jean-Baptiste Leca from the Primate Research Institute in Kyoto, Japan
assessed social learning exhibited by these macaques during
stone-handling, a behavior that has been passed down from elder to
younger since it was observed in some of the troops in 1979.
Stone-handling, in this study, included rubbing and clacking stones
together, pounding them onto hard surfaces, picking them up, and
cuddling, carrying, pushing, rolling and throwing them.

The scientists found, for example, that an infant's proximity to
their mother had a significant impact on the development of the
infant's stone-handling abilities. In other words, infants with mothers
who frequently exhibited stone-handling behaviors spent more time with
their mother, about 75% of their time, during the first three months of
life, and they also participated in stone-handling earlier in life than
the other infants. These findings suggest that the mothers' frequent
stone-handling caught the infants' attention, and as a result, the
infants acquired the behavior more quickly than other infants.

Furthermore, as the primatologists reported in the December 2008
issue of Current Directions in Psychological Science, the
stone-handling behavior changed with each generation as individual
macaques contributed their own patterns of stone-handling, such as
stone-throwing.

"The recent emergence of a unique behavior, stone-throwing, may
serve to augment the effect of intimidation displays," concluded the
authors. "Research on such transformation may shed light on the
evolution of stone-tool use in early hominids."